finetune: Prevent fc overflow #304
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fc is a int16, check limits before setting.
WesleyAC
requested changes
Nov 19, 2023
| @@ -197,7 +198,14 @@ bool finetune_face_loop(movement_event_t event, movement_settings_t *settings, v | |||
| finetune_adjust_subseconds(250); | |||
| } else if (finetune_page == 2 && finetune_get_hours_passed() >= 6) { | |||
| // Applying ppm correction, only if >6 hours passed | |||
| nanosec_state.freq_correction += (int)round(finetune_get_correction() * 100); | |||
| int32_t f = nanosec_state.freq_correction + (int)round(finetune_get_correction() * 100); | |||
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I think a cleaner approach is something like:
int correction = (int)round(finetune_get_correction() * 100);
if (nanosec_state.freq_correction > 0 && correction > SHRT_MAX - nanosec_state.freq_correction) {
nanosec_state.freq_correction = SHRT_MAX;
} else if (nanosec_state.freq_correction < 0 && correction < SHRT_MIN - nanosec_state.freq_correction) {
nanosec_state.freq_correction = SHRT_MIN;
} else {
nanosec_state.freq_correction += correction;
}since it avoids the need for a intermediate variable. Does that look right to you?
|
Possible solution: get the compiler to do this for us by using integer overflow builtins. |
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fc is a int16, check limits before setting.
I have a watch with a really bad oscillator, and setting with finetune will actually go beyond int16 and roll over to negative. I was confused for a while until I finally realized the problem. Added a check in finetune to prevent this from happening. I believe my watch has too big of an error for FREQCORR to correct, but that is another issue.